Field of Art
The present disclosure relates to image forming apparatuses configured to form images.
Description of the Related Art
An electrophotographic image forming apparatus includes a fixing device configured to fix a toner image transferred onto a sheet. The fixing device fixes the toner image with heat and pressure using a fixing member which includes a heat source and a pressing member which is pressed against the fixing member.
In recent years, an increasing number of image forming apparatuses employ a film-heating fixing device for prompt activation and energy conservation. The film-heating fixing device includes a ceramic heater as a heating member and a pressing roller as a pressing member, and a fixing film as a heat transmission member is sandwiched between the ceramic heater and the pressing roller to form a pressure nip portion. Then, a sheet onto which an unfixed toner image is transferred is introduced and nipped and conveyed to fix the unfixed toner image onto the sheet with pressing force of the pressure nip portion while heat of the ceramic heater is applied via the fixing film.
In the fixing device, if the fixing film and the pressing roller are in contact with each other for a long time, components of the fixing film and the pressing roller can be deformed, which can cause an image failure such as image unevenness. A known method for preventing such an image failure is to execute control such that the fixing member and the pressing member are separated when no operation of forming an image is executed. Japanese Patent Application Laid-Open No. 2000-122460 discusses an image forming apparatus including a mechanism for separating a fixing member and a pressing member. The image forming apparatus executes a separation operation using the mechanism to separate the fixing member and the pressing member from each other at a predetermined timing, such as a timing at which an image-forming state is changed to a non-image-forming state or a timing at which a jam is caused. In this way, the above-described image failure associated with deformation of the fixing member is prevented. Further, Japanese Patent Application Laid-Open No. 2009-58664 discusses a method in which a separation operation is performed if a predetermined time passes since the end of an image formation operation.
The image forming apparatus discussed in Japanese Patent Application Laid-Open No. 2009-58664 executes a fixing separation operation uniformly regardless of the state of the apparatus after the predetermined time passes since the end of the image formation operation. Thus, for example, the following problem can arise.
Suppose that, for example, the image forming apparatus is in a standby state when the predetermined time passes since the end of the image formation operation. Being in the standby state indicates that the entire apparatus is standing by for a start of image formation. While the entire apparatus is standing by for a start of image formation, if the fixing member and the pressing member of the fixing device are separated, a preparation operation for changing from the separated state to a contact state is needed, and this becomes a bottleneck that delays a start of image formation. As a result, the first copy output time (FCOT) is increased.